#include <stdio.h>
#include <stdbool.h>
#include <math.h>
#define N 3009
int arr[N];
bool check(double num,double n)
{
	if(num*num*num<=n)return true;
	else return false;
}
int main()
{
	double n=9214748364889878999;
	//scanf("%lf",&n);
	double l=-1,r=2500000;
	while(l+1e-8<r)
	{
		double mid=(l+r)/2;
		if(check(mid,n))l=mid;
		else r=mid;
	}
	printf("%lf\n",l);
	//printf("%lf\n",pow(n,1.0/3));
	
    return 0;
}
